1、網路拓撲

 2、基礎IP配置

R1：
enable
config t
no ip domain lookup
line console 0
no exec-timeout
logging synchronous
exit


interface f0/0
no shutdown
ip add 1.1.123.1 255.255.255.224
exit

interface loopback 0
ip add 10.10.1.1 255.255.255.0
no shutdown
exit
end


R2：
enable
config t
no ip domain lookup
line console 0
no 
 
exec-timeout
logging synchronous
exit


interface f0/0
no shutdown
ip add 1.1.123.2 255.255.255.224
exit

interface s1/0
no shutdown
ip add 1.1.24.1 255.255.255.248
exit

interface loopback 0
ip add 10.10.2.2 255.255.255.0
no shutdown
exit
end


R3：
enable
config t
no ip domain lookup
line console 0
no exec-timeout
logging synchronous
exit


interface f0
 
/0
no shutdown
ip add 1.1.123.3 255.255.255.224
exit


interface s1/1
no shutdown
ip add 1.1.34.2 255.255.255.248
exit

interface loopback 0
ip add 10.10.3.3 255.255.255.0
no shutdown
exit
end

R4 ：
enable
config t
no ip domain lookup
line console 0
no exec-timeout
logging synchronous
exit


interface s1/0
no shutdown
ip add 
 
1.1.24.2 255.255.255.248
exit

interface s1/1
no shutdown
ip add 1.1.34.2 255.255.255.248
exit

interface s1/2
no shutdown
ip add 1.1.45.2 255.255.255.0
exit

interface loopback 0
no shut
ip address 10.10.4.4 255.255.255.0
end


R5 ：
enable
config t
no ip domain lookup
line console 0
no exec-timeout
logging synchronous
exit

interface s1/2
no shutdown
ip add 1.1.45.2 255.255.255.0
exit

interface loopback 0
no shut
ip add 10.10.5.5 255.255.255.0
end

 3、在R4與R5之間配置PPP封裝

R5#show interfaces s1/2
Serial1/2 is up, line protocol is up 
  Hardware is M4T
  Internet address is 1.1.45.2/24
  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation HDLC, crc 16, loopback not set                     /××××思科交換機埠之間預設封裝格式是HDLC*****/
  Keepalive set (10 sec)
  Restart-Delay is 0 secs
  Last input 00:00:08, output 00:00:07, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/0 (size/max total/threshold/drops) 
     Conversations  0/1/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 1158 kilobits/sec
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     69 packets input, 5292 bytes, 0 no buffer
     Received 69 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     79 packets output, 6371 bytes, 0 underruns
     0 output errors, 0 collisions, 3 interface resets

R4

R4(config)#interface s1/2
R4(config-if)#encapsulation ppp
R4(config-if)#exit
R4(config)#
*Nov 29 08:19:08.775: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/2, changed state to down          /*****當兩側封裝格式不一致時，埠Down***/
R4(config)#

R5

R5#config t
Enter configuration commands, one per line. End with CNTL/Z.
R5(config)#interface s1/2
R5(config-if)#encapsulation ppp
R5(config-if)#
R5(config-if)#
R5(config-if)#
*Nov 29 08:21:32.191: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/2, changed state to up  /*****當兩側封裝格式一致時，埠再次UP***/
R5(config-if)#